﻿using System;
using System.Collections.Generic;
using System.Drawing;
using System.Drawing.Imaging;
using System.IO;
using System.Linq;
using System.Security.Cryptography;
using System.Text;
using System.Web;
using NPOI.SS.Formula.Functions;

namespace Common
{
    /// <summary>
    /// 图片验证码生成类
    /// </summary>
    public class ImgVCodeHelper
    {
        #region 私有字段  
        private string text;  
        private Bitmap image;
        private byte[] byteImage;
        //private int letterCount = 4;   //验证码位数  
        private int letterWidth = 25;  //单个字体的宽度范围  
        private int letterHeight = 40; //单个字体的高度范围  
        private static byte[] randb = new byte[4];  
        private static RNGCryptoServiceProvider rand = new RNGCryptoServiceProvider();
        private Font[] fonts =
        {
            new Font(new FontFamily("Times New Roman"), 14 + Next(1), System.Drawing.FontStyle.Regular),
            new Font(new FontFamily("Georgia"), 14 + Next(1), System.Drawing.FontStyle.Regular),
            new Font(new FontFamily("Arial"), 14 + Next(1), System.Drawing.FontStyle.Regular),
            new Font(new FontFamily("Comic Sans MS"), 14 + Next(1), System.Drawing.FontStyle.Regular)
        };
        #endregion  
 
        #region 公有属性  
        /// <summary>  
        /// 验证码  
        /// </summary>  
        public string Text  
        {  
            get { return this.text; }  
        }  
  
        /// <summary>  
        /// 验证码图片  
        /// </summary>  
        public Bitmap Image  
        {  
            get { return this.image; }  
        }

        /// <summary>
        /// byte[]格式的图片验证码
        /// </summary>
        public byte[] ByteImge
        {
            get { return this.byteImage; }  
        }

        #endregion  
 
        #region 构造函数  
        public ImgVCodeHelper()  
        {  
            HttpContext.Current.Response.Expires = 0;  
            HttpContext.Current.Response.Buffer = true;  
            HttpContext.Current.Response.ExpiresAbsolute = DateTime.Now.AddSeconds(-1);  
            HttpContext.Current.Response.AddHeader("pragma", "no-cache");  
            HttpContext.Current.Response.CacheControl = "no-cache";  
            this.text = RandomHelper.Number(4);  
            CreateImage();  
        }  
        #endregion  
 
        #region 私有方法  
        /// <summary>  
        /// 获得下一个随机数  
        /// </summary>  
        /// <param name="max">最大值</param>  
        private static int Next(int max)  
        {  
            rand.GetBytes(randb);  
            int value = BitConverter.ToInt32(randb, 0);  
            value = value % (max + 1);  
            if (value < 0) value = -value;  
            return value;  
        }  
  
        /// <summary>  
        /// 获得下一个随机数  
        /// </summary>  
        /// <param name="min">最小值</param>  
        /// <param name="max">最大值</param>  
        private static int Next(int min, int max)  
        {  
            int value = Next(max - min) + min;  
            return value;  
        }  
        #endregion  
 
        #region 公共方法  
        /// <summary>  
        /// 绘制验证码  
        /// </summary>  
        public void CreateImage()  
        {  
            int int_ImageWidth = this.text.Length * letterWidth;  
            Bitmap image = new Bitmap(int_ImageWidth, letterHeight);  
            Graphics g = Graphics.FromImage(image);  
            g.Clear(Color.White);  
            for (int i = 0; i < 2; i++)  
            {  
                int x1 = Next(image.Width - 1);  
                int x2 = Next(image.Width - 1);  
                int y1 = Next(image.Height - 1);  
                int y2 = Next(image.Height - 1);  
                g.DrawLine(new Pen(Color.Silver), x1, y1, x2, y2);  
            }  
            int _x = -12, _y = 0;  
            for (int int_index = 0; int_index < this.text.Length; int_index++)  
            {  
                _x += Next(12, 16);  
                _y = Next(-2, 2);  
                string str_char = this.text.Substring(int_index, 1);  
                str_char = Next(1) == 1 ? str_char.ToLower() : str_char.ToUpper();  
                Brush newBrush = new SolidBrush(GetRandomColor());  
                Point thePos = new Point(_x, _y);  
                g.DrawString(str_char, fonts[Next(fonts.Length - 1)], newBrush, thePos);  
            }  
            for (int i = 0; i < 10; i++)  
            {  
                int x = Next(image.Width - 1);  
                int y = Next(image.Height - 1);  
                image.SetPixel(x, y, Color.FromArgb(Next(0, 255), Next(0, 255), Next(0, 255)));  
            }  
            image = TwistImage(image, true, Next(1, 3), Next(4, 6));  
            g.DrawRectangle(new Pen(Color.LightGray, 1), 0, 0, int_ImageWidth - 1, (letterHeight - 1));

            //转换图片格式为byte[]
            MemoryStream stream = new MemoryStream();
            image.Save(stream, ImageFormat.Jpeg);

            this.byteImage = stream.ToArray();
            this.image = image;  
        }  
  
        /// <summary>  
        /// 字体随机颜色  
        /// </summary>  
        public Color GetRandomColor()  
        {  
            Random RandomNum_First = new Random((int)DateTime.Now.Ticks);  
            System.Threading.Thread.Sleep(RandomNum_First.Next(50));  
            Random RandomNum_Sencond = new Random((int)DateTime.Now.Ticks);  
            int int_Red = RandomNum_First.Next(180);  
            int int_Green = RandomNum_Sencond.Next(180);  
            int int_Blue = (int_Red + int_Green > 300) ? 0 : 400 - int_Red - int_Green;  
            int_Blue = (int_Blue > 255) ? 255 : int_Blue;  
            return Color.FromArgb(int_Red, int_Green, int_Blue);  
        }  
  
        /// <summary>  
        /// 正弦曲线Wave扭曲图片  
        /// </summary>  
        /// <param name="srcBmp">图片路径</param>  
        /// <param name="bXDir">如果扭曲则选择为True</param>  
        /// <param name="nMultValue">波形的幅度倍数，越大扭曲的程度越高,一般为3</param>  
        /// <param name="dPhase">波形的起始相位,取值区间[0-2*PI)</param>  
        public System.Drawing.Bitmap TwistImage(Bitmap srcBmp, bool bXDir, double dMultValue, double dPhase)  
        {  
            double PI = 6.283185307179586476925286766559;  
            Bitmap destBmp = new Bitmap(srcBmp.Width, srcBmp.Height);  
            Graphics graph = Graphics.FromImage(destBmp);  
            graph.FillRectangle(new SolidBrush(Color.White), 0, 0, destBmp.Width, destBmp.Height);  
            graph.Dispose();  
            double dBaseAxisLen = bXDir ? (double)destBmp.Height : (double)destBmp.Width;  
            for (int i = 0; i < destBmp.Width; i++)  
            {  
                for (int j = 0; j < destBmp.Height; j++)  
                {  
                    double dx = 0;  
                    dx = bXDir ? (PI * (double)j) / dBaseAxisLen : (PI * (double)i) / dBaseAxisLen;  
                    dx += dPhase;  
                    double dy = Math.Sin(dx);  
                    int nOldX = 0, nOldY = 0;  
                    nOldX = bXDir ? i + (int)(dy * dMultValue) : i;  
                    nOldY = bXDir ? j : j + (int)(dy * dMultValue);  
  
                    Color color = srcBmp.GetPixel(i, j);  
                    if (nOldX >= 0 && nOldX < destBmp.Width  
                     && nOldY >= 0 && nOldY < destBmp.Height)  
                    {  
                        destBmp.SetPixel(nOldX, nOldY, color);  
                    }  
                }  
            }  
            srcBmp.Dispose();  
            return destBmp;  
        }  
        #endregion  
    }
}
